UIWANG, South Korea – December 23 – The Korea Railroad Research Institute (KRRI) (President: Sagong Myung) has developed an “EPDM Pad Sleeper,” which mitigates train-induced impact on ballasted tracks, extends maintenance intervals, and reduces the required ballast layer thickness. Following field performance testing on the Gyeongbu Line, the technology successfully passed the Korea National Railway’s KR railway facility performance verification.
* EPDM (Ethylene Propylene Diene Monomer): A highly durable synthetic rubber

The EPDM pad sleeper affixes an embedded synthetic rubber pad (6 mm thick) to the bottom surface of a concrete sleeper, reducing pressure transmission to the ballast layer (trackbed*) by 20–30%. This reduces ballast wear and breakage, thereby lowering maintenance work and associated costs.
* Trackbed: The ballast layer laid beneath railway tracks

This technology was developed to reduce labor and maintenance costs associated with ballasted track maintenance. It is drawing particular attention as an efficient alternative for lines such as the first phase of the Gyeongbu High-Speed Railway, where scheduled maintenance cycles for ballasted tracks are approaching.

By maintaining ballast quality in good condition for extended periods, the technology reduces the frequency of ballasted track maintenance. Beyond ballast preservation, it also mitigates deterioration of other track components such as rails and sleepers, thereby extending their service life.

KRRI developed two types of EPDM pad sleepers for ballasted tracks—high-stiffness and medium-stiffness—and completed structural reviews through numerical analysis, full-scale testing, and field tests (Osong Test Line, Gyeongbu Line).

Structural stability assessments and field test results confirmed safe train operation under conditions including KTX operation at speeds of 250 km/h and heavy-load freight train operation.

In addition, through impact load tests, full-scale tests reproducing train dynamic loads*, and long-term field installation tests at the Osong Test Line over a period of four years and six months, KRRI verified that the application of pad sleepers reduces ballast breakage, increases lateral ballast resistance, and lowers ballast pressure, thereby confirming train operation safety of EPDM pad sleepers.
* Dynamic load: Impact force applied during movement

In October 2023, KRRI conducted field installation tests on the operating section between Jeondong and Seochang stations on the Gyeongbu Line (located in Sejong City). After more than two years and one month of operation, both safe train operation and improved pad performance have been confirmed throughout the entire section equipped with pad sleepers. Based on these verification results, the EPDM pad sleeper technology passed the Korea National Railway's railway facility performance verification in July this year.

This technology was developed through KRRI’s basic research program under the National Research Council of Science & Technology (NST) (Chairman: Kim Young-sik), titled “Development of Long-Life Ballasted Track Technology Using EPDM Pad Sleepers.”

Principal Researcher Kim Dae-sang at KRRI said, “The EPDM pad sleeper is a cost-effective technology that reduces the maintenance burden of conventional ballasted tracks. Based on the performance verified through field validation, we will further specify the commercialization stage.”

President Sagong Myung of KRRI stated, “This research represents an achievement that enhances train operation safety while contributing to environmentally friendly railway operations. We will continue to take the lead in developing practical, field-oriented technologies with sustainability in mind.”





Press Contacts

Sunghyun Baek
Korea Railroad Research Institute
baeksh@krri.re.kr
+82 31 460 5162